The present invention relates to the field of angioplasty. In particular, the present invention relates to an intravascular catheter, such as a dilatation balloon catheter, of the type which is advanced over a guide wire and which has a guide wire lumen extending longitudinally over a portion of the length of the catheter adjacent the distal end of the catheter. This type of dilatation balloon catheter is generally referred to as a rapid exchange or single operator exchange catheter.
The placement of a dilatation balloon across a stenosis in a coronary artery can be a difficult procedure. Movement of the elongated dilatation balloon catheter (typically about 135 cm) is achieved by manual manipulation of its proximal end outside the patient. The ability of a catheter to bend and advance through the vasculature is commonly referred to as the "trackability" of the catheter. "Pushability" refers to the ability of the catheter to transmit the longitudinal forces applied by the physician along the catheter shaft to advance the distal end of the catheter through a coronary artery to and across the stenosis. Preferably, a catheter has a low profile, and is relatively trackable and pushable.
One common type of dilatation catheter has a separate guide wire lumen in the catheter so that a guide wire can be used to establish the path through the stenosis. The dilatation catheter can then be advanced over the guide wire until the balloon on the catheter is positioned within the stenosis. A recognized deficiency with this type of catheter is evident when it is desired to replace an existing catheter with another catheter. In that instance, the physician prefers to maintain the position of the guide wire in the patient's vascular system relative to the stenosis as the catheter is withdrawn over the guide wire. In the event of an abrupt closure of a partially dilated lesion when the balloon catheter has been withdrawn after an initial dilatation, the wire will maintain the path through the lesion. Any significant or uncontrolled movement of the exposed guide wire is avoided, so that the guide wire does not become dislodged from its position across the lesion.
In order to exchange a catheter with a guide wire lumen that extends the entire length of the catheter shaft, a longer exchange wire is sometimes exchanged for the standard guide wire, or a guide wire extension may be provided. The use of long exchange wires or guide wire extensions present a great length of guide wire outside the patient which must then be managed during the catheter exchange procedure. This not only proves awkward but typically requires two persons.
Rapid exchange catheter designs have overcome this problem. A first type of rapid exchange catheter includes a distal guide wire lumen which extends from a distal end of the catheter through the inside of the dilatation balloon and then exits the catheter at a point proximal of the balloon. This type of catheter is disclosed by Keith et al. in U.S. Pat. No. 5,217,482. With this design, catheter exchanges can be accomplished by a single operator with a guide wire which extends proximally outside of the patient's body only slightly more than the length of the distal guide wire lumen.
A rapid exchange catheter can be withdrawn without removing the guide wire from across the stenosis or utilizing a guide wire extension or extra long guide wire.
In utilizing a rapid exchange catheter, the guide wire is first grasped near the proximal end of the guide catheter. The catheter is then withdrawn until the proximal opening of the guide wire lumen is reached. The grasping hand is then moved incrementally away from the proximal opening of the guide wire lumen on the catheter. The catheter is then incrementally withdrawn until the catheter is fully removed from the guide catheter and the guide wire is thus again exposed and accessible adjacent to the proximal end of the guide catheter.
Once the initial catheter has been completely removed from the guide wire, a second catheter can be loaded onto the guide wire by inserting the proximal end of the guide wire into a distal opening of the guide wire lumen in the second catheter. This second catheter is then advanced by "feeding" the catheter distally over the guide wire while holding the guide wire stationary. The proximal end of the guide wire will then emerge out of the proximal opening of the distal guide wire lumen and is accessible again for gripping by the physician. By holding onto the exposed portion of the guide wire in this manner, the second catheter can then be advanced distally along the stationary guide wire to a desired position in the patient's vasculature.
A second type of rapid exchange catheter is constructed with the entire distal guide wire lumen adjacent the distal tip of the catheter (distally of the intravascular interoperative device (e.g., dilatation balloon) on the catheter). An apparatus having this configuration is described in U.S. Pat. No. 5,395,332, incorporated herein by reference. This structural design allows for a smaller catheter profile in the balloon area because a tube having a guide wire lumen extending therethrough does not have to be incorporated through the balloon. Further, the guide wire contacts the vessel wall during inflation of the balloon.
The short guide wire tube distal of the balloon does not, however, allow the guide wire to provide support for the catheter in the balloon area. Thus, without additional structure to provide rigidity along the catheter shaft and through the balloon, the pushability of the catheter can be reduced.
Buchbinder et al., in U.S. Pat. No. 5,267,958, disclose a rapid exchange balloon catheter having a body and one or more loops external to the body and spaced from the balloon for insertion of a guide wire. In one embodiment, Buchbinder et al. disclose a loop for the guide wire located proximally of the balloon, and a second loop located distally of the balloon with the guide wire extending through both of these loops. Buchbinder et al. assert that this design overcomes the deficiencies with the rapid exchange catheters that have a loop or ring which is located only distally of the balloon. Thus, the pushability and tracking of the device is asserted to be improved. Alternatively, Buchbinder et al. disclose a rapid exchange catheter wherein the guide wire fits through a sleeve which is located around the body of the catheter proximally of the balloon.
As depicted in FIG. 5 of Buchbinder et al., a first keeper is mounted on the catheter body proximal to the balloon, and a second keeper is mounted distally to the balloon. In use, Buchbinder et al. teaches that once the catheter is in place, the guide wire may be withdrawn from the second keeper to a position proximal of the balloon before the balloon is inflated. In this way, it is believed that the guide wire does not restrict the expansion of the balloon or become pressed into the stenosis upon inflation of the balloon. However, with the design of Buchbinder et al., once the guide wire has been retracted out of the second keeper which is distal of the balloon, it would be extremely difficult to reinsert the guide wire across the stenosis and through the second keeper or distal keeper. Thus, it may be difficult to return the guide wire to its position across the stenosis in order to perform a catheter exchange.
Kontos et al., in U.S. Pat. No. 5,180,367, disclose a procedure and apparatus for such procedure, whereby a small balloon catheter can be placed in a patient's body, expanded and collapsed as needed, and then a second larger balloon catheter placed over the smaller one. In FIG. 5, Kontos et al. depict an embodiment, wherein a sliding guide means begins at tip 58, terminates at 62, immediately adjacent the proximal end of chamber 36 (see, column 6, lines 45-50). In this embodiment, the sliding guide means 60 runs along the outside of the membrane 34. With this embodiment, it is clear that a guide wire could not be retracted to a point proximal of the balloon and reinserted due to the termination of the tube prior to the proximal end of the balloon. As such, it would be difficult to return the guide wire to its position across the stenosis in order to perform a catheter exchange.